Cointainer.kt

import kotlin.reflect.KClass

fun main() {
    start {
        factory<Client>{ FakeClient() }
        factory<Service>{ FakeService(get()) }
    }

    val service: Service by inject()
    service.call()
}

typealias AppDeclaration = Container.() -> Unit

object ContextHandler {
    var container: Container? = null

    fun register(container: Container) {
        this.container = container
    }

    fun get() = container
}

fun start(declaration: AppDeclaration) {
    val container = Container()
    ContextHandler.register(container)
    declaration.invoke(container)
}

typealias Definition<T> = () -> T

class Container {
    val definitions = HashMap<KClass<*>, Definition<*>>()

    inline fun <reified T> factory(noinline value: Definition<T>) {
        definitions[T::class] = value
    }

    inline fun <reified T> get() = definitions[T::class]?.invoke() as T
}


inline fun <reified T>  inject(): Lazy<T> = lazy(LazyThreadSafetyMode.NONE) {
    val container = ContextHandler.get()
    container?.get<T>()!!
}

////////////////// General App
interface Service {
    fun call()
}

interface Client {
    fun request()
}

class FakeService(val client: Client): Service {
    override fun call() {
        println("Calling the service")
        client.request()
    }
}

class FakeClient: Client {
    override fun request() {
        println("doing the request")
    }
}